There is accumulating evidence of the benefits of dietary intake of the long chain omega-3 fatty acids found in fish, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). These fatty acids have been shown to decrease the risk of coronary heart disease and ischemic heart disease in large epidemiological studies.
Omega-3 fatty acids have furthermore been proposed for a variety of medical uses, including prevention of heart disease, diabetes, inflammation, depression, Alzheimer's and attention deficit disorder. Examples of pharmaceuticals based on omega-3 fatty acids include Lovaza® (known also as Omacor®) which is approved in various countries for treatment of patients with very high triglycerides (hypertriglyceridemia), and for post myocardial infarction adjuvant treatment in secondary prevention after myocardial infarction. In Lovaza® the omega-3 fatty acids are present as ethyl esters. Each Lovaza® 1 gram capsule contains 465 mg EPA ethyl ester, 375 mg DHA ethyl ester, 80 mg of other omega-3 fatty acids, 30 mg of omega-6 fatty acids and 50 mg of antioxidants.
Vascepa® (AMR-101) is a further approved pharmaceutical based on omega-3 fatty acids. Vascepa® capsules contain EPA omega-3 fatty acid in the form of ethyl eicosapentaenoic acid. Vascepa® has been clinically proven to significantly reduce triglyceride levels without increasing LDL-C. It has been approved in the United States for use as an adjunct to diet to reduce triglyceride levels in adult patients with severe (≧500 mg/dL) hypertriglyceridemia.
There is growing evidence, however, that the molecular form of omega-3 fatty acids (e.g. triglycerides or ethyl esters) might be of importance for their biological effect and for their distribution in the body. Krill oil contains a high proportion of omega-3 fatty acids incorporated in phospholipids and it has been demonstrated that krill oil had stronger effects than fish oil on specific parameters related to metabolic syndromes [1]. The authors suggest that this difference may be linked to differences in the incorporation of omega-3 fatty acids into membranes. Further, it was demonstrated that the level of DHA in the brain increased significantly after krill oil administration when compared to control animals [2]. Thus, omega-3 fatty acids incorporated in phospholipids may be differently distributed in the body compared to omega-3 fatty acids in other molecular forms.
The concentration of phospholipids in commercially available krill oils is relatively low. For example, they can include high amounts of neutral lipids and free fatty acids. Although krill extracts with 90% phospholipid have been described [3], these contain undesirable components such as lysophospholipids and astaxanthins, and their preparation has involved the use of solvent systems which are not favourable for downstream pharmaceutical use. Thus there is a need for krill phospholipid compositions having a high purity without retaining pharmaceutically undesirable solvents or components, and also for processes by which such compositions can be prepared.